Gas feeding device for controlled vaporization of an organanometallic compound used in deposition film formation

ABSTRACT

A gas-feeding device for feeding a starting gas for deposition-film-formation by the chemical vapor deposition method, comprising a container having a space for discharging the starting gas containing an organometallic compound by introduction of a carrier gas; a gas-introducing means connected to the container for introducing a carrier gas is described. A plurality of openings for introducing the organometallic compound into the container is also provided, wherein each opening is part of an atomizer employing a piezoelectric element to eject the organometallic compound in a mist state into the container where the carrier gas passes through the space, and a container is provided for storing the organometallic compound.

This application is a division of application Ser. No. 08/232,431 filedApr. 21, 1994, now U.S. Pat. No. 5,476,547, which is a continuation ofapplication Ser. No. 08/041,340 filed Apr. 1, 1993, now abandoned, whichis a continuation of application Ser. No. 07/869,121 filed Apr. 15,1992, now abandoned, which is a continuation of application Ser. No.07/586,877 filed Sep. 24, 1990, which is now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a deposition-film-forming apparatus anda gas feeding device. In particular, the present invention relates to agas-feeding device which is suitable for feeding an organometalliccompound-containing starting gas or the like in a thin-film depositionapparatus by the chemical vapor deposition (CVD) method.

2. Related Background Art

A chemical vapor deposition method using an organometallic compound isemployed widely for the deposition of a metal thin-film or asemiconductor thin-film of III-V groups. The widely used organometallicstarting materials, trimethylgallium (TMG) and trimethylaluminum (TMA),are liquid at room temperature. By the flow of a carrier gas like argon,which is introduced through a tube inserted into the liquidorganometallic compound, the liquid organometallic compound istransported in a vapor state to a reaction vessel constituting a spacefor forming the deposited film.

FIG. 7 illustrates a conventional gas feeding device for transporting agas (a starting gas) containing an organometallic compound. Anorganometallic compound 2 is stored in a liquid state in a metalliccontainer 1. A carrier gas 6, such as argon, is blown as bubbles intothe liquid through a metal pipe 41 which is inserted into theorganometallic compound, 2. The organometallic compound brought into thebubbles in a saturated vapor state, is transported as the starting gas 7to a reaction vessel (not shown) through a pipe 42 which is not insertedinto the liquid. For example, with an inserted pipe 41, having adiameter of 1/4 inch and having a carrier gas flow rate of from 1 to 100sccm, an organometallic compound such as TMG and TMA can be transportedin an amount corresponding to the saturated vapor pressure in thecarrier gas that is outgoing from the outlet pipe 42.

However, for improving productivity, namely for constituting adeposition-film-forming apparatus, which is capable of depositing a thinfilm on a plurality of substrates at the same time, a large amount ofstarting gas is correspondingly required. If a large flow rate of thecarrier gas, as much as from 1 to 10 1/min, is introduced through onemetal pipe 41, as shown in FIG. 7, the organometallic compound will notbe saturated sufficiently in the bubbles, so that the quantity of thetransported organometallic compound will not increase, even if the flowrate of the carrier gas is increased. In particular, for a viscousorganometallic compound, the bubbles formed by the metal pipe 41 becomeslarge in size, causing a pulsation of a discharged gas flow, or in anextreme case, the bubbles may come to join together to form a tubulargas flow path which reaches to the gas layer above the liquid surface.For example, with a metal pipe 41 having 1/4 inch diameter, the carriergas flow path may change at a flow rate of around 100 cc/min from abubble form to a tubular form, resulting in a disproportionality betweenthe amount of the transported organometallic compound and the flow ratethe carrier gas.

Accordingly, for transportation in a high flow rate, use of a pluralityof containers for containing the organometallic compound may beconsidered. For example, for a required amount of the carrier gas offrom 1 to 10 1/min, 10 to 100 containers are required on the assumptionthat 100 cc/min of the carrier gas can be introduced per container. Insuch a case, problems may be involved because of a size increase in theapparatus, a rise in the cost, and complications in maintenance.

On the other hand, Japanese Patent Laid-open Application No.sho-62-33769 discloses the perforation of a number of holes at the tipof the metal tube. This may be effective for an organometallic compoundhaving a low viscosity such as TMG, but cannot always be effective foran organometallic compound having a high viscosity.

Japanese Patent Laid-open Application No. sho-62-207870 discloses theinstallation of an ultrasonic wave generator having a magnetostrictiveoscillator coupled onto an organic metallic compound containingcontainer. In an example thereof, a metal pipe for introducing a carriergas is inserted into the compound in a gas phase. However, thegeneration of mist by the ultrasonic effect cannot be expected becausethe container generally contains little of the gas which causescavitation. Although a description is found in the patent publicationthat the metal pipe for the carrier introduction may be inserted intothe organometallic compound, a sufficient cavitation effect cannot beexpected in viscous organometallic compounds because bubbles are notreadily generated when the carrier gas has a high flow rate as mentionedabove.

Further, for the case of organometallic compounds having a low viscositylike TMG, the above-cited Japanese Patent Laid-open Application No.sho-62-207870 shows a method for transporting TMG effectively at a highflow rate. This method, however, is not so effective for organometalliccompounds like DMAH (dimethylaluminum hydride) having a high viscosity.This is because no measure is taken during the introduction of a carriergas for the formation of minute bubbles in the organometallic compound.

Japanese Patent Laid-open Application No. sho-60-131973 discloses amethod for vaporizing a liquid organometallic compound by bubbling thegas in such a manner that the gas is ejected through a bubble-formingdevice having a plurality of gas-ejecting holes at the tip of the gasejection portion. Even with this method, however, there may be someinstability during the feeding of the gaseous organometallic compoundfor the vaporization of a large amount of the organometallic compoundfor rapid formation of a deposition film because bubbles which arecaused by introduction of a large amount of gas, combine mutually toform even larger bubbles that splash out of the liquid organometalliccompound, the splashing being caused by the bursting of the largerbubbles, and the resulting accumulation of the liquid in a feed pipe.

As discussed above, there has been no satisfactory gas feeding devicefor feeding a large amount of a starting gas employing an organometalliccompound having a high viscosity.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a gas feeding deviceand a deposition-film-forming apparatus which do not involve thedisadvantage of a size increase of the apparatus and are capable oftransporting a large amount of starting gas even with viscousorganometallic compounds.

Another object of the present invention is to provide a gas-feedingdevice and a deposition-film-forming apparatus which is capable oftransporting a large quantity of an alkylaluminum hydride in high puritywhich is suitable for satisfactorily conducting a good deposition filmformation.

According to an aspect of the present invention, there is provided agas-feeding device for feeding a starting gas fordeposition-film-formation by the chemical vapor deposition method,comprising a container having a space for discharging the starting gas,containing an organometallic compound by introduction of a carrier gas;a gas-introducing means connected to the container and having aplurality of gas-introducing openings for introducing the carrier gas orthe starting gas into the container to generate the starting gas; and agas generation-accelerating means for accelerating the generation of thestarting gas.

According to another aspect of the present invention, there is provideda gas feeding device for feeding a starting gas fordeposition-film-formation by the chemical vapor deposition methodcomprising an organometallic compound-storing means for discharging thestarting gas containing the organometallic compound by introduction of acarrier gas; a plurality of gas-introducing members for introducing thecarrier gas into the storing means; and a gas switching means forturning on or turning off feed lines of the carrier gas connected to theplurality of gas-introducing members, and for distributing the carriergas through the turned-on feed line.

According to still another aspect of the present invention, there isprovided a gas-feeding device for feeding a starting gas fordeposition-film-formation by the chemical vapor deposition methodcomprising an organometallic compound-storing means for discharging thestarting gas containing the organometallic compound by introduction of acarrier gas; a gas-introducing member having a plurality of smallopenings for introducing the carrier gas into the storing means; and anultrasonic oscillator arranged in the storing means.

According to a further aspect of the present invention, there isprovided a gas-feeding device for feeding a starting gas fordeposition-film-formation by the chemical vapor deposition methodcomprising a container, having a space for discharging the starting gas,containing an organometallic compound by introduction of a carrier gas;and an injection means for injecting the organometallic compound in amist state into the container.

According to a still further aspect of the present invention, there isprovided a deposition-film-forming apparatus for the chemical vapordeposition method comprising:

(1) a gas-feeding device comprising a container having a space forintroducing and discharging a starting gas containing an organometalliccompound for formation of deposition film by aid of a carrier gas; agas-introducing means connected to the container and having a pluralityof gas-introducing openings for introducing the the carrier gas or thestarting gas into the container to generate the starting gas; and a gasgeneration-accelerating means for accelerating the generation of thestarting gas;

(2) a reaction chamber connected to the gas-feeding device to receivethe starting gas fed therein, and (3) an exhausting means connected tothe reaction chamber for exhausting the reaction chamber.

According to a still further aspect of the present invention, there isprovided a deposition-film-forming apparatus for the chemical vapordeposition method comprising:

(1) a gas feeding device comprising an organometallic compound-storingmeans for discharging the starting gas containing the organometalliccompound by introduction of a carrier gas for deposition film formation;a plurality of gas-introducing members for introducing the carrier gasinto the storing means; and a gas switching means for turning on orturning off feed lines of the carrier gas to the plurality ofgas-introducing means, and distributing the carrier gas through theopened feed line,

(2) a reaction chamber connected to the gas-feeding device to receivethe starting gas fed therein, and (3) an exhausting means connected tothe reaction chamber for exhausting the reaction chamber.

According to a still further aspect of the present invention, there isprovided a deposition-film-forming apparatus for the chemical vapordeposition method comprising:

(1) a gas feeding device comprising an organometallic compound-storingmeans for discharging the starting gas containing the organometalliccompound by introduction of a carrier gas for deposition film formation;a gas-introducing member having a plurality of openings for introducingthe carrier gas into the storing means; and a ultrasonic oscillatorinstalled in the storing means,

(2) a reaction chamber connected to the gas-feeding device to receivethe starting gas fed therein, and (3) an exhausting means connected tothe reaction chamber for exhausting the reaction chamber.

According to a still further aspect of the present invention, there isprovided a deposition-film-forming apparatus for the chemical vapordeposition method comprising:

(1) a gas feeding device comprising a container having a space fordischarging the starting gas containing an organometallic compound byintroduction of a carrier gas for deposition film formation; and aninjection means for injecting the organometallic compound in a miststate into the container,

(2) a reaction chamber connected to the gas-feeding device to receivethe starting gas fed therein, and (3) an exhausting means connected tothe reaction chamber for exhausting the reaction chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an example of the gas-feedingdevice of the present invention.

FIG. 2 is a timing chart for explaining a method for driving the device.

FIG. 3 is a schematic diagram illustrating another example of thegas-feeding device of the present invention.

FIG. 4 is a schematic diagram illustrating a still another example ofthe gas-feeding device of the present invention.

FIGS. 5A to 5D are schematic diagrams for explaining the mechanism ofpreferable selective formation of the deposition film by using thegas-feeding device of the present invention.

FIG. 6 is a schematic diagram of a deposition-film-forming apparatus towhich the gas-feeding device of the present invention is applicable.

FIG. 7 is a schematic diagram of a conventional gas-feeding apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferable gas-feeding devices of the present invention are as describedbelow.

The gas-feeding device of the present invention comprises a container,having a space for discharging the starting gas, containing anorganometallic compound by introduction of a carrier gas; agas-introducing means connected to the container and having a pluralityof gas-inlets for introducing the the carrier gas or the starting gasinto the container to generate the starting gas; and a gasgeneration-accelerating means for accelerating the generation of thestarting gas.

The gas-feeding device of the present invention is capable of feeding alarge quantity of a starting gas stably by employing a plurality of thegas-introducing openings and gas generation-accelerating means. Thegas-feeding device of the present invention is capable of transporting alarge quantity of starting gas even with a viscous organometalliccompound without causing the problem of a disadvantageous size increaseof the apparatus.

The deposition-film-forming apparatus of the present invention comprisesthe aforementioned gas-feeding device, a reaction chamber connected tothe gas-feeding device to receive the starting gas fed therein, and agas-exhausting means connected to the reaction chamber to exhaust thereaction chamber.

The deposition-film-forming apparatus comprising the gas-feeding deviceof the present invention is capable of stably feeding a large quantityof a starting gas into the reaction chamber, allowing the formation of adeposition film of high quality at a high deposition rate.

An example of the present invention is described in detail by referringto the figures.

As described later, dimethyl aluminum hydride (DMAH) gives a deposit ofAl or an Al--Si alloy of high quality merely by a thermal reaction on asurface of an electron-donating material by using hydrogen as a reactiongas. The vapor pressure of the DMAH is approximately 1 Torr at roomtemperature, so that it is readily transported in comparison with TIBA(vapor pressure: approximately 0.1 Torr at room temperature) which hasbeen used as the starting material for Al in CVD.

In the case of a deposition-film-forming apparatus according to thevacuum CVD method, in mass production, the amount of the carrier gasused is required to be as large as 1 to 10 L/min. DMAH, which has a highviscosity, has a couple of problems. Either the transporting gas flowtends to become pulsated resulting in a hindrance of the continuoustransportation, or the gas flow becomes tubular as mentioned before.

Accordingly, this example has the constitution below.

FIG. 1 illustrates an example of the constitution of the gas-feedingdevice of the present invention.

The metallic container 10 is made of SUS. The inside surface of themetallic container is preferably coated with SiO₂ or the like becauseorganometallic compounds such as DMAH and TMA will decompose at a metalsurface in the presence of hydrogen even at room temperature to form anunnecessary alkane such as methane and the like. At the bottom of thecontainer 10, a plurality of pipes are arranged in a horizontaldirection at approximately equal distances with the gas dischargingopenings directed upwards. A carrier gas 6 is introduced from an inletpipe 4 to form bubbles 3. The vapor of the organometallic compound 2 istransported along with the carrier gas through an outlet pipe 5 to areaction vessel (see FIG. 6). A gas-switch 19 selects the gasintroduction routes from pipes 11-17 inserted into the organometalliccompound 2 to introduce the carrier gas fed from the inlet pipe 4 topipes 11-17 in pulse with delays in timing. The gas-switch isconstituted, for example, of valve bodies placed in connection withportions of the respective pipes such as electromagnetic valves operatedby electric current; an effector for the valves; and a control means forthe effector. Although seven pipes are shown in FIG. 1, the number ofthe pipes may be more or less than seven. The timing for switching isadjusted depending on the length of each pipe (11-17) from the gasswitch 19 to the outlets. In this example, the gas-switch 19 serves as agas-generation-accelerating means.

FIG. 2 shows a timing pattern for the introduction of the carrier gas tothe pipes 11-17. In FIG. 2, the hatched portions show the time offlowing of the gas in the respective pipes. The flow rates in therespective pipes are adjusted to be equal at any time. In correspondencewith the dimension of the pipes, the time T₁ and T₂ is determined sothat the bubbles formed by the carrier gas in the organometalliccompound may not communicate the outlets with the gas layer. In thetiming chart of FIG. 2, the carrier gas flows through 6 pipes at anytime as the simplest example, where one sixth of the carrier gasintroduced through the inlet pipe 4 is distributed to each of the sixpipes of the pipes 11-17.

In the case where the pipes have respectively one opening, the quantityof the carrier gas introduced into the respective pipes 11-17 ispreferably not more than 100 cc/min for DMAH. In a more preferableexample, where plural small openings, not a single opening, are providedfor each tip of the pipes 11-17, the carrier gas flow rate in each pipemay be larger than 100 cc/min. When small openings of n in number areprovided in each pipe, then the carrier gas flow rate in each of thepipes is up to n×100 cc/min. Specifically, for each of the pipes 11-17of 3/8 inch or 1/4 inch in diameter, the number is more preferably notmore than 10. If the number is larger, then there is a high probabilitythat the formed bubbles may combine with each other. At any rate, ameasure should be taken so that the bubbles ejected from the tip of thepipe may not join together to form a tubular gas phase communicatingwith the above gas layer.

In the device shown in FIG. 1, bubbles are formed sequentially from therespective pipes 11-17 nearly continuously as a whole without pulsationof the starting gas 7 discharged from outlet pipe 5.

By use of the gas-feeding device of the example, the size of bubblesfrom the respective openings can be made smaller by appropriateselection of the flow rate of the carrier gas introduced through theplural gas-introducing means and intermittent feed of the carrier gas toa respective gas-introducing member with a recess time of T₂, wherebythe organometallic compound can be vaporized sufficiently into the gas,and a large quantity of the starting gas can be fed.

FIG. 3 shows another example of the constitution of the gas-feedingdevice of the present invention.

The metallic container 10 is made of SUS. The inside surface of themetallic container is preferably coated with SiO₂ or the like because anorganometallic compound such as DMAH, and TMA will decompose at a metalsurface in the presence of hydrogen even at room temperature to form anunnecessary alkane such as methane and the like.

A plurality of a small openings 5 are provided for gas discharge on themetal pipe 4 inserted in a organometallic compound. A carrier gas 9 isejected through each of the small openings. The small openings may beprovided either at a uniform interval or at irregular intervals. Thepipe 4 inserted in the organometallic compound, although illustrated inlinear form in FIG. 3, may be in a circular form or in a serpentine formso as to distribute the positions of the openings uniformly in theorganometallic compound container 10.

In particular, if the organometallic compound 2 is DMAH having a highviscosity, the carrier gas flow rate through the respective smallopenings 5 is preferably not more than 100 sccm. A larger flow rate than100 sccm may destroy the bubbles of the carrier gas ejected from thesmall openings, forming an open gaseous path from the small openings tothe surface of the organometallic compound in a tubular form, which mayretard the cavitation effect generated by a supersonic oscillatoremployed in this example. The ultrasonic oscillation produces acavitation effect to generate fine bubbles, and effectively forms a mistof the organometallic compound from the surface of the organometalliccompound. The ultrasonic oscillator may be provided in pluralityirrespectively of the one ultrasonic oscillator 8 in FIG. 3. Moreover,the ultrasonic oscillator may be installed on a side face of theorganometallic compound container 10. In this example, the ultrasonicoscillator 8 serves as a gas-generation-accelerating means for formingthe starting gas effectively.

In this example, small openings are provided and a limited flow rate ofcarrier gas 9, ejected from each of the small openings realizes thegeneration of fine bubbles in the organometallic compound and theformation of mist on the liquid surface. However, the effectivegeneration of fine bubbles cannot be achieved sufficiently by only byproviding the small openings. In particular, for a viscousorganometallic compound like DMAH, it is desirable for the carrier gasto be ejected from the respective small openings continuously and at aflow rate lower than a certain level.

In this example, DMAH having a high viscosity can be transported by thecarrier gas 9 flowing out from the organometallic compound contained inthe metallic container 10 containing an amount corresponding to thesaturated vapor pressure of DMAH by limiting the flow rate of thecarrier gas ejected from small openings 5 to approximately 100 sccm andemploying a cavitation effect of ultrasonic oscillation, even when thetotal carrier gas introduced to the metallic container 10 is in anamount as large as 10 slm (standard liter per minute).

No method has hitherto been found for effectively transporting anorganometallic compound by such a large amount of a carrier gas. Inparticular, in the vacuum CVD method, the number of wafers used in onedeposition batch depends on the efficiency of the transportation of alarge a mount of viscous DMAH. The use of the gas-feeding device of thepresent invention in a deposition-film-forming apparatus shown later inFIG. 6 makes feasible the deposition of an Al or Al--Si thin film on100-200 wafers of 4 inches in one deposition batch at a high depositionrate.

In the gas-feeding device shown in the present example, a mist of anorganometallic compound is generated by a great number of fine bubblesor by a gas phase in the organometallic compound-storing means byselecting appropriately the carrier gas flow rate for each small opening(e.g., approximately 100 sccm or less), and further by causingcavitation by an ultrasonic oscillator installed in the metalliccontainer containing the organometallic compound, thereby theorganometallic compound can be contained in the carrier gas ejected fromthe container in an amount corresponding to the saturated vaporpressure.

A still another example of the constitution of the gas-feeding device ofthe present invention is illustrated in FIG. 4.

An organometallic compound is stored in a liquid state in a metalliccontainer 31. A gas is introduced through nozzles 30. Atomizers 34(piezoelectric atomizers) employing a piezoelectric element as anejection-energy-generating means spray the organometallic compound drawnup from the metallic container 31 in a mist state into a metallicchamber 33. The piezoelectric atomizer 34 is preferably provided inplural numbers. Five atomizers are provided in the example in FIG. 4.The atomizers 34 are connected to a driving circuit (DR) for supplying adriving signal to be controlled by the driving circuit. In this example,the piezoelectric atomizers 34 serve as a gas-generation-acceleratingmeans for generating the starting gas effectively.

The organometallic compound is ejected in a size of several μm or lessin a mist state from the piezoelectric atomizers 34. Although theatomizers 34 are installed at the bottom of the metallic chamber 33 inthe figure, they may be installed at the side face of the chamber. Anatomizer other than the piezoelectric type may also be used.

The inside wall of the metallic chamber 33 is preferably coated with aninsulating material such as SiO₂ or the like because an organometalliccompound such as TMA and DMAH will decompose at a metal surface of SUSin the presence of hydrogen even at room temperature, to form anunnecessary alkane such as methane and the like.

In such a device, a carrier gas 6 such as hydrogen, argon, nitrogen, andthe like is introduced through an inlet pipe 37. The carrier gas comesto contain the organometallic compound in an amount corresponding to thesaturated vapor pressure while passing through the metallic chamberwhere the organometallic compound is sprayed in a mist state, and flowsout from an outlet pipe 39 as a starting gas 7. The organometalliccompound is in a mist state, having a size of several μm or less, and iscontained in the carrier gas effectively.

The organometallic compound that has attached itself to the inside faceof the metallic chamber 33 is recovered through a recovery pipe 36 tothe metallic container 31 containing the organometallic compound.

The use of a piezoelectric atomizer allows spraying in a mist state evenif the organometallic compound has a high viscosity, so that theorganometallic compound can be contained in a carrier gas effectivelyand independently of the viscosity of the organometallic compound. Sincethe carrier gas does not pass through a liquid, there is no fluctuationof the flow rate of the carrier gas 7 containing the organometalliccompound. Thus pulsation of the flow can be completely prevented insteadof being caused in the transportation of an organometallic compound ofhigh viscosity. By the method of transporting an organometallic compoundof this constitution, the transportation of DMAH can be effected in thestate that the carrier gas contains DMAH in an amount corresponding tothe saturated vapor pressure thereof, even if the total flow rate of thecarrier gas is as much as 10 slm (standard liter per minute).

No method has hitherto been found for transporting effectively anorganometallic compound by such a large amount of carrier gas. Inparticular, in the conventional vacuum CVD method employing DMAH, thenumber of wafers usable in one deposition batch depends on theefficiency of transportation of a large amount of viscous DMAH. The useof the gas-feeding device of the present invention in adeposition-film-forming apparatus, shown later in FIG. 6, makes feasiblethe deposition of an Al or Al--Si thin film on 100-200 wafers of 4inches in one deposition batch at a high deposition rate.

The gas-feeding device shown in the example transports an organometalliccompound in a liquid state from a container storing the organometalliccompound, and ejects the liquid organometallic compound in a mistthrough an ejection means like a piezoelectric nozzle into a space,thereby discharging an introduced gas which contains the organometalliccompound in an amount corresponding to the saturated vapor pressurethereof.

The gas-feeding device described above is suitably used with adeposition-film-forming apparatus described below.

FIG. 6 illustrates a schematic sectional view of adeposition-film-forming apparatus of the present invention.

An external reaction tube 50 made of quartz forms a substantiallyenclosed space for deposition film formation. In the interior, aplurality of substrates 57 for formation of a metal film mainlyconstituted of aluminum, silicon or the like as the deposition film arefixed by a substrate holder 56 at a predetermined position. An internalreaction tube 51 made of quartz separates the gas flow in the externalreaction tube 50. A metallic flange 54 closes or opens an opening of theexternal reaction tube 50. The substrates 57 are placed in the substrateholder 56 arranged in the interior reaction tube 51. The substrateholder 56 is preferably made of quartz.

In this apparatus, the temperature of the substrates is controlled by aheater 59. The pressure in the reaction tube 50 is controlled by anexhausting system connected through a gas exhausting outlet 53.

The apparatus shown by FIG. 6 has a mixer 62 which is connected with afirst gas system for a gas fed from a gas-feeding device 60, and asecond gas system for H₂ or the like, and further a third gas system forSi₂ H₆ or the like, from which the resulting starting gas mixture isintroduced through a starting-gas-introducing pipe 52 into the reactiontube 50. The starting gas reacts at the surface of the substrates 57while passing through the inside of the interior reaction tube 51 asshown by arrow marks 58 in FIG. 6, resulting in deposition of Al orA--Si on the substrate surface. The gas after the reaction passesthrough a space formed by the internal reaction tube 51 and the externalreaction tube 50 and is exhausted from an exhausting outlet 53.

To take in or out the substrates, the metallic flange 54 is loweredtogether with the substrate holder 56 and the substrates 57 by means ofan elevator (not shown in the figure) to move it to a predeterminedposition.

With such an apparatus under the aforementioned deposition-film-formingconditions, satisfactory Al or Al--Si film can be formed simultaneouslyon all wafers in the apparatus.

As described above, the gas-feeding device of the present invention isparticularly suitable for apparatuses for forming deposition films byuse of an organometallic compound having a high viscosity like DMAH in alarge amount. Naturally, the kind of the organometallic compounds, theconstitution of the deposition-film-forming apparatuses or the likematters are not limited to the above examples.

According to the present invention, excellent deposition films can beformed in a large quantity at a high production rate since the presentinvention enables the stable transportation of a large amount ofstarting gas without problems such as size increase of the apparatuseven when an organometallic compound having a high viscosity isemployed. Thus the production cost of the semiconductor device can bereduced remarkably.

Specifically, the gas-feeding device illustrated in FIG. 1 is suitablyapplied to an apparatus for the vacuum CVD method illustrated, forexample, in FIG. 6 which is capable of holding a large number of wafers(substrates) at a time and depositing Al or Al--Si. Since the depositionof Al or Al--Si undergoes by a surface reaction at a heatedelectron-donating substrate surface, Al or Al--Si can be deposited fromDMAH and H₂ (or further with an Si starting gas such as Si₂ H₆) by a hotwall type of the vacuum CVD method in which the substrate only isheated.

In the film formation, Al or Al--Si deposits to a thickness of 100-200 Åonly on an electron-donating substrate under conditions of a reactiontube pressure of from 10⁻³ to 760 Torr, a substrate temperature of from270° to 350° C., DMAH partial pressure of from 1×10⁻⁵ to 1.3×10⁻³ timesthe reaction tube pressure, (or further Si₂ H₆ partial pressure of from1×10⁻⁷ to 1×10⁻⁴ time the reaction tube pressure). For improvement offilm thickness uniformity in wafers, the reaction tube pressure ispreferably from 5×10⁻² to 5 Torr, and the DMAH partial pressure ispreferably from 1.3×10⁻⁵ to 1.3×10⁻⁴ times the reaction tube pressure.The preferable substrate temperature is from 270° to 300° C. forsuppressing surface migration and preparing satisfactory continuousfilm.

Further, the gas-feeding device illustrated in FIG. 3 is also suitablyapplied to an apparatus for the vacuum CVD method illustrated, forexample, in FIG. 6 which is capable of holding a large number of wafers(substrates) at a time and depositing Al or Al--Si. Since the depositionof Al or Al--Si undergoes by a surface reaction at a heatedelectron-donating substrate surface, Al or Al--Si can be deposited fromDMAH and H₂ (or further with an Si starting gas such as Si₂ H₆) by a hotwall type vacuum CVD method in which only the substrate is heated.

In the film formation, Al or Al--Si deposits to a thickness of 100-200 Åonly on an electron-donating substrate under conditions of the reactiontube pressure of from 10⁻³ to 760 Torr, the substrate temperature offrom 270° to 350° C., DMAH partial pressure of from 1×10⁻⁵ to 1.3×10⁻³times the reaction tube pressure, (or further Si₂ H₆ partial pressure offrom 1×10⁻⁷ to 1×10⁻⁴ times the reaction tube pressure). For improvementof film thickness uniformity in wafers, the reaction tube pressure ispreferably from 5×10⁻² to 5 Torr, and the DMAH partial pressure ispreferably from 1.3×10⁻⁵ to 1.3×10⁻⁴ times the reaction tube pressure.The preferable substrate temperature is from 270° to 300° C. forsuppressing surface migration and preparing satisfactory continuousfilm.

Still further, the gas-feeding device illustrated in FIG. 4 is alsosuitably applied to an apparatus for the vacuum CVD method illustrated,for example, in FIG. 6 which is capable of holding a large number ofwafers (substrates) at a time and depositing Al or Al--Si. Since thedeposition of Al or Al--Si undergoes by a surface reaction at a heatedelectron-donating substrate surface, Al or Al--Si can be deposited fromDMAH and H₂ (or further with an Si starting gas such as Si₂ H₆) by a hotwall type of the vacuum CVD method in which the substrate only isheated.

In the film formation, Al or Al--Si deposits to a thickness of 100-200 Åonly on an electron-donating substrate under conditions of the reactiontube pressure of from 10⁻³ to 760 Torr, the substrate temperature offrom 270° to 350° C., DMAH partial pressure of from 1×10⁻⁵ to 1.3×10⁻³times the reaction tube pressure, (or further Si₂ H₆ partial pressure offrom 1×10⁻⁷ to 1×10⁻⁴ times the reaction tube pressure). For improvementof film thickness uniformity, the reaction tube pressure is preferablyfrom 5×10⁻² to 5 Torr, and the DMAH partial pressure is preferably from1.3×10⁻⁵ to 1.3×10⁻⁴ times the reaction tube pressure. The preferablesubstrate temperature is from 270° to 300° C. for suppressing surfacemigration and preparing satisfactory and continuous film.

The method for deposition film formation, namely, the CVD methodutilizing an alkylaluminum hydride, particularly an alkylaluminumhydride having a methyl group is described in detail.

In this method, a gas containing an organometallic compound,specifically ##STR1## is used as a starting gas containing at least oneatom to be a constitutional element of the deposition film, or further agas containing a Si atom as a starting gas, or further additionallyhydrogen as the starting gas are used. An Al or Al--Si film is formedselectively on the substrate by vapor deposition.

The substrate applicable to this method has a first substrate surfacematerial for providing a surface for deposition of Al or Al--Si, and asecond substrate surface material for non-deposition of Al or Al--Si.The first substrate surface material is composed of an electron-donatingsubstance.

The electron-donating property is explained in detail.

An electron-donating material is such a material that free electronsexist or a free electron is intentionally formed in the substrate: forexample, while a material having a surface on which a chemical reactionis accelerated by electron transfer with a starting gas moleculeadhering on the substrate surface. Generally, metals and semiconductorsare the examples. Metals and semiconductors having extremely thin oxidefilm on the surface are included thereto, since the electron transferbetween the substrate and the adhered starting molecule occurs to causethe chemical reaction if the oxide film is extremely thin.

Specific examples thereof are semiconductors such as single crystallinesilicon, polycrystalline silicon, amorphous silicon and the like; III-Vgroup compound semiconductor and II-VI group compound semiconductorcomposed of binary, ternary or quaternary combinations of Ga, In, and Alas the Group III element and P, As, and N as the group V element; metalsper se such as tungsten, molybdenum, tantalum, aluminum, titanium,copper, and the like; silicides of the above metals such as tungstensilicide, molybdenum silicide, tantalum silicide, aluminum silicide,titanium silicide, and the like; and metals containing any one of theabove metal such as aluminum silicon, aluminum titanium, aluminumcopper, aluminum tantalum, aluminum silicon copper, aluminum silicontitanium, aluminum palladium, titanium nitride, and the like.

On the other hand, the materials having a surface on which Al or Al--Sidoes not selectively deposit, namely non-electron-donating materialsinclude usual insulating materials; silicon oxide formed by thermaloxidation, CVD, etc.; glass or oxide films such as BSG, PSG, BPSG, andthe like; prepared by the thermal CVD, plasma CVD, vacuum CVD, ECR-CVDmethods; and the like materials.

On the substrate of such constitution, Al or Al--Si deposits by only asimple thermal reaction in a reaction system of a starting gas andhydrogen. For example, the thermal reaction in the reaction system ofDMAH and hydrogen is considered basically as below: ##STR2##

The DMAH has a dimer structure at a room temperature. The addition ofSi₂ H₆ or the like causes formation of Al--Si alloy because the Si₂ H₆having reached to the substrate surface decomposes by a surface chemicalreaction and the resulting Si is incorporated into the film. From MMAH₂also, high quality Al could be deposited. However, MMAH₂, which has avapor pressure as low as 0.01 to 0.1 Torr, cannot readily be transportedin a large amount, thereby the upper limit of the deposition rate beingseveral hundred Å/min or below. Therefore DMAH, which has a vaporpressure of 1 Torr at room temperature, can preferably be used.

The aluminum film prepared by the above method assumes a single crystalstructure, excellent in surface smoothness, anti-migrationcharacteristics, etc., having low resistance and superiorcharacteristics for wiring and use of electrodes.

In the deposition of an aluminum film from an alkylalumninum hydride,the temperature of the substrate is selected within the range of fromthe decomposition temperature of alkylaluminum hydride to be used to450° C., more preferably from 200° to 350° C., still more preferablyfrom 270° C. to 350° C.

The mechanism of aluminum deposition is considered as described belowreferring FIG. 5 at the moment.

When DMAH reaches, with its methyl group directed to the substratesides, a substrate in a state that hydrogen atoms are attached on anelectron-donating substrate, namely on a substrate having electrons(FIG. 5A), the electron on the substrate cuts a bond between aluminumand a methyl group (FIGS. 5B and 5C). The reaction is as below.

    (CH.sub.3).sub.2 AlH+2H+2e→2CH.sub.4 ↑+Al--H

The similar reaction proceeds with hydrogen remaining on aluminum thathas deposited and free electrons (FIG. 5D). If hydrogen atoms aredeficient, a hydrogen molecule, being the starting gas, decomposes tosupply hydrogen atoms. On the contrary, on a non-electron-donatingsurface, the above reaction does not proceed owing to lack of electrons,causing no deposition of aluminum. Incidentally, FIGS. 5A to 5D are toaid understanding of the reaction mechanism, so that the numbers of H, eand Al are not consistent

Examples of an experiment regarding gas transportation by using agas-feeding device of the present invention are described below.

EXPERIMENTAL EXAMPLE 1

Into an organometallic compound contained in the metallic container 10of FIG. 1, hydrogen gas was introduced through the metallic pipe 4 at aflow rate of L sccm. By utilizing the gas switch 19, hydrogen gas wasfed to each of the pipes 11-17 at a flow rate of (L/6) sccm in pulse ata timing shown in FIG. 2. Into each pipe, the gas was fed for a time ofT₁ and the gas was stopped for a time of T₂. The partial pressure ofDMAH was measured in the gas 7 flowing out from the outlet pipe 5 atvaried T₁ and T₂.

As shown in Table 1, even at the flow rate of hydrogen gas of 600 sccm,the DMAH was contained at a partial pressure of 1 Torr in the outgoinghydrogen gas, which is equal to the saturated vapor pressure at roomtemperature. The variation of flow rate of the outgoing hydrogen gas waswithin 1%.

                  TABLE 1                                                         ______________________________________                                        L (sccm) 100    100    300  300  600  600  800  800                           T.sub.1 (sec)                                                                           30    60      30  60    30  60   30   60                            T.sub.2 (sec)                                                                           5     10      5   10    5   10   5    10                            DMAH partial                                                                            1      1      1    1    1    1   0.8  0.8                           pressure (Torr)                                                               ______________________________________                                    

EXPERIMENTAL EXAMPLE 2

Measurements were made in the same manner as in Experimental example 1except that argon gas was used in place of hydrogen. The results weresimilar to those in Table 1. Even at the flow rate of 600 sccm, the DMAHwas transported with the outgoing argon gas at a partial pressure equalto its saturated vapor pressure.

EXPERIMENTAL EXAMPLE 3

In FIG. 1, a metal pipe having five small openings was used as the tipof the respective pipes 11-17. Into an organometallic compound containedin the metallic container 10, hydrogen gas was introduced through ametallic pipe 4 at a flow rate of L sccm. By utilizing the gas switch19, hydrogen gas was fed to each of the pipes 11-17 at a flow rate of(L/6) sccm in pulse at a timing shown in FIG. 2. Into each pipe, the gaswas fed for time T₁ and the gas was stopped for time T₂. The partialpressure of DMAH was measured in the gas 7 flowing out from the outletpipe 5 at varied T₁ and T₂.

As shown in Table 2, even at the flow rate of hydrogen gas of 3000 sccm,the DMAH was contained at a partial pressure of 1 Torr in the outgoinghydrogen gas, which is equal to the saturated vapor pressure at roomtemperature. The variation of flow rate of the outgoing hydrogen gas waswithin 1%.

The carrier gas may be an inert gas, nitrogen gas, hydrogen gas, etc.For aluminum deposition, hydrogen gas is especially preferable sincehydrogen atoms affect directly the aluminum deposition.

                  TABLE 2                                                         ______________________________________                                        L (sccm) 300    300    900  900  3000 3000 4000 4000                          T.sub.1 (sec)                                                                           30    60      30  60    30   60  30   60                            T.sub.2 (sec)                                                                           5     10      5   10     5   10  5    10                            DMAH partial                                                                            1      1      1    1     1    1  0.8  0.8                           pressure (Torr)                                                               ______________________________________                                    

EXPERIMENTAL EXAMPLE 4

A gas-feeding device illustrated in FIG. 3 was employed. In the device,the metal pipe 4 inserted in the organometallic compound had 100 smallopenings 5. Hydrogen gas 6 is introduced through the metal pipe 4 at aflow rate of L slm. The DMAH partial pressure contained in the hydrogengas 7 flowing out from the outlet pipe 5 was measured.

As shown in Table 3, even at the flow rate of hydrogen gas of 10 slm,the DMAH was contained at a partial pressure of 1 Torr in the outgoinghydrogen gas, which is equal to the saturated vapor pressure at roomtemperature. The variation of flow rate of the outgoing hydrogen gas waswithin 1%.

                  TABLE 3                                                         ______________________________________                                        L (slm)    0.5      1.5   5.0     10.0 12.0                                   DMAH partial                                                                             1        1     1       1    0.8                                    pressure (Torr)                                                               ______________________________________                                    

EXPERIMENTAL EXAMPLE 5

Measurements were made in the same manner as in Experimental example 4except that argon gas was used in place of hydrogen. The results weresimilar to those in Table 3. Even at the flow rate of 10 slm, the DMAHwas transported with the outgoing argon gas at a partial pressure equalto its saturated vapor pressure.

The gas-feeding device employed in this experimental example was foundto be preferably applicable to a deposition-film-forming apparatus ofvacuum CVD for selective deposition of an Al or Al--Si film of superiorquality on a substrate as an electroconductive deposition film in thesame way as the gas-feeding device employed in Experimental example 1.

EXPERIMENTAL EXAMPLE 6

A device illustrated in FIG. 4, in which five piezoelectric atomizers 34were installed, was used for transporting an organometallic compound,DMAH. Hydrogen gas 6 is introduced through the metal pipe 37 at a flowrate of L slm. The DMAH partial pressure of the hydrogen gas wasmeasured flowing out from the outlet pipe 9.

As shown in Table 4, even at the flow rate of hydrogen gas of 10 slm,the DMAH was contained at a partial pressure of 1 Torr in theflowing-out hydrogen gas, which is equal to the saturated vapor pressureat room temperature. The variation of flow rate of the outgoing hydrogengas was within 1%.

                  TABLE 4                                                         ______________________________________                                        L (slm)    0.5      1.5   5.0     10.0 12.0                                   DMAH partial                                                                             1        1     1       1    0.8                                    pressure (Torr)                                                               ______________________________________                                    

EXPERIMENTAL EXAMPLE 7

Measurements were made in the same manner as in Experimental example 6except that argon gas was used in place of hydrogen. The results weresimilar to those in Table 4. Even at the flow rate of 10 slm, the DMAHwas transported with the outgoing argon gas at a partial pressure equalto its saturated vapor pressure.

The gas-feeding device employed in this experimental example was foundto be preferably applicable to a deposition-film-forming apparatus ofvacuum CVD for selective deposition of an Al or Al--Si film of superiorquality on a substrate as an electroconductive deposition film in thesame way as the gas-feeding device employed in Experimental examples1-5.

What is claimed is:
 1. A gas-feeding device for feeding a starting gasfor formation of a deposited film by the chemical vapor depositionmethod, comprising a first container having an inlet for introducing acarrier gas into the first container, a space for discharging a startinggas containing an organometallic compound and an outlet for feeding thestarting gas from the space to the outside of the first container, theoutlet being provided in a position opposite to the inlet; a pluralityof ejection means each having an opening for ejecting the organometalliccompound in a mist state with the carrier gas into the space, theplurality of election means being provided at a lower part of the firstcontainer; a second container for storing the organometallic compound tobe fed to the ejection means; and a passage to enable the first and thesecond containers to communicate with each other.
 2. The gas-feedingdevice of claim 1, wherein a means for generating energy for theejection means is a piezoelectric element.
 3. The device according toclaim 1 wherein the organometallic compound comprises a hydridecontaining aluminum.
 4. The device according to claim 3 wherein theorganometallic compound comprises dimethyl aluminum hydride.
 5. Thedevice according to claim 1 wherein the organometallic compound has avapor pressure of about 1 Torr or less at room temperature.
 6. Thedevice according to claim 1 wherein the device further comprises acarrier gas-feeding source connected to the container which can feed thecarrier gas at a rate of 1 to 10 liters per minute.
 7. Adeposited-film-forming apparatus for forming a deposited film by thechemical vapor deposition method, comprising:(1) a gas-feeding devicecomprising a first container having an inlet for introducing a carriergas into the first container, a space for discharging a starting gascontaining an organometallic compound and an outlet for feeding thestarting gas from the space to the outside of the first container, theoutlet being provided in a position opposite to the inlet, a pluralityof ejection means each having an opening for ejecting the organometalliccompound in a mist state with the carrier gas into the space, theplurality of ejection means being provided at a lower part of the firstcontainer, a second container for storing the organometallic compound tobe fed to the ejection means, and a passage to enable the first and thesecond containers to communicate with each other; (2) a reaction chamberconnected to the gas-feeding device to receive the starting gas fed fromthe gas-feeding device; and (3) an exhausting means connected to thereaction chamber for exhausting the reaction chamber.
 8. The apparatusaccording to claim 7 wherein the organometallic compound comprises ahydride containing aluminum.
 9. The apparatus according to claim 8wherein the organometallic compound comprises dimethyl aluminum hydride.10. The apparatus according to claim 7 wherein the organometalliccompound has a vapor pressure of about 1 Torr or less at roomtemperature.
 11. The apparatus according to claim 7 wherein theapparatus further comprises a carrier gas-feeding source connected tothe container which can feed the carrier gas at a rate of 1 to 10 litersper minute.
 12. A gas-feeding device for feeding a starting gas forformation of a deposited film by the chemical vapor deposition method,comprising a first container having an inlet for introducing a carriergas into the first container, a space for discharging a starting gascontaining an organometallic compound and an outlet for feeding thestarting gas to the outside of the first container, the outlet beingprovided at a side of the first container toward which the carrier gasadvances; a second container for storing the organometallic compound; apassage connected to a lower part of the first container and to thesecond container for recovering the organometallic compound from thefirst container to the second container; a gas-introducing meansconnected to the first container for introducing a carrier gas; aplurality of openings for introducing the organometallic compound withthe carrier gas into the first container, the plurality of openingsbeing provided at a lower part of the first container, wherein each ofsaid openings is a part of an atomizer employing a piezoelectric elementto eject the organometallic compound in a mist state toward a lineconnecting the inlet with the outlet in the first container along whichthe carrier gas passes through the space.
 13. The device according toclaim 12 wherein the organometallic compound comprises a hydridecontaining aluminum.
 14. The device according to claim 13 wherein theorganometallic compound comprises dimethyl aluminum hydride.
 15. Thedevice according to claim 12 wherein the organometallic compound has avapor pressure of about 1 Torr or less at room temperature.
 16. Thedevice according to claim 12 wherein the device further comprises acarrier gas-feeding source connected to the gas-introducing means whichcan feed the carrier gas at a rate of 1 to 10 liters per minute.
 17. Adeposited-film-forming apparatus for forming a deposited film by thechemical vapor deposition method, comprising:(1) a gas-feeding devicefor feeding a starting gas comprising: a first container having an inletfor introducing a carrier gas into the first container, a space fordischarging a starting gas containing an organometallic compound and anoutlet for feeding the starting gas to the outside of the firstcontainer, the outlet being provided at a side of the first containertoward which the carrier gas advances; a second container for storingthe organometallic compound; a passage connected to a lower part of thefirst container and to the second container for recovering theorganometallic compound from the first container to the secondcontainer; a gas-introducing means connected to the first container forintroducing a carrier gas; a plurality of openings for introducing theorganometallic compound with the carrier gas into the first container,the plurality of openings being provided at a lower part of the firstcontainer, wherein each of said openings is a part of an atomizeremploying a piezoelectric element to eject the organometallic compoundin a mist state toward a line connecting the inlet with the outlet inthe first container along which the carrier gas passes through thespace; (2) a reaction chamber connected to the gas-feeding device toreceive the starting gas fed from the gas-feeding device; and (3) anexhausting means connected to the reaction chamber for exhausting thereaction chamber.
 18. The apparatus according to claim 17 wherein theorganometallic compound comprises a hydride containing aluminum.
 19. Theapparatus according to claim 18 wherein the organometallic compoundcomprises dimethyl aluminum hydride.
 20. The apparatus according toclaim 17 wherein the organometallic compound has a vapor pressure ofabout 1 Torr or less at room temperature.
 21. The apparatus according toclaim 17 wherein the apparatus further comprises a carrier gas-feedingsource connected to the gas-introducing means which can feed the carriergas at a rate of 1 to 10 liters per minute.